The present invention relates to a quick release coupling for the crank of a bicycle drive train. Bicycles of a variety of sizes, styles and structures are abundant and extremely well known. Such bicycles have numerous ways of assembling their component parts.
In the ownership of a bicycle, it is often necessary and desirable to be able to quickly disassemble and assemble component parts, not only to change or upgrade individual component parts, but for purposes of cleaning, oiling, greasing and other maintenance.
In a bicycle, the standard means of propulsion consists of a front sprocket coupled to a rear sprocket by a closed loop chain. The front sprocket typically includes an axle coupled thereto to which opposed crank arms are assembled, with the crank arm on one side being displaced 180° with respect to the orientation of the other crank. At the respective ends of the cranks, pedals are mounted.
Over the course of use of a bicycle, if the owner does not keep up with the maintenance, it is often the case that interconnected component parts become more and more difficult to disassemble for maintenance purposes. Additionally, even if the bicycle is properly maintained, it is often advantageous to be able to quickly and efficiently disassemble parts for maintenance, as well as for storage and repair purposes.
There is a need for an easy means for assembling and disassembling the crank with respect to the front sprocket and its axle. For such a means to be effective and advantageous, it must best facilitate the transfer of force from the pedals of the bicycle to the front sprocket. In other words, the coupling between the crank arm and the front sprocket must be such that the transfer of force is steady and secure. It is with these needs in mind that the present invention was developed. It is also noted that the inventive quick release coupling is useful in releasably coupling any crank to a shaft.
Applicant is aware of the following prior art:    U.S. Pat. No. 4,171,822 to Thun    U.S. Pat. No. 5,060,537 to Nagano    U.S. Pat. No. 5,203,229 to Chen    U.S. Pat. No. 5,586,472 to Lin    U.S. Pat. No. 6,477,917 to Peyre et al.    U.S. Pat. No. 6,708,998 to Blake    U.S. Pat. No. 6,968,754 to Bandarra    U.S. Pat. No. 7,104,158 to Harrington    U.S. Pat. No. 7,350,796 to Misevski    U.S. Pat. No. 8,061,236 to French    U.S. Published Application No. 2003/0188602 to Lubanski    U.S. Published Application No. 2009/0205462 to Harrington.
Of the above-listed prior art, Thun discloses an attachment between a crank and an axle consisting of an elongated rod having an irregular cross-section which is rotated to couple the crank to the axle. Nagano teaches a locking mechanism to attach a pedal to a crank that includes a rotating cam. The other references include attachment means including set screws, threaded fasteners, hexagonal cross-section shafts, spring biased pins, and other fastening means. The present invention differs from the teachings of all of these prior art references as contemplating an attachment means which includes a crank shaft of circular cross-section with a keyway machined therein to allow torque transfer between the shaft and a crank having an opening with a tab designed to couple with the keyway, and a bayonet-type lock that employs the keyway to align itself with a thrust locking groove and the ability to rotate to a locked position, whereupon a screw or other threaded fastener may be employed to lock the bayonet lock in the locked position to maintain the crank on the drive shaft.